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        <h2>
          <span class="refentrytitle">fofilter</span>
        </h2>
        <p>fofilter — 
      Formant filter.
    </p>
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      <div class="refsect1">
        <a id="idp110231664"></a>
        <h2>Description</h2>
        <p>
Fofilter generates a stream of overlapping sinewave grains, when fed with 
a pulse train. Each grain is the impulse response of a combination of 
two BP filters. The grains are defined by their attack time (determining 
the skirtwidth of the formant region at -60dB) and decay time 
(-6dB bandwidth). Overlapping will occur when 1/freq &lt; decay, but, 
unlike FOF, there is no upper limit on the number of overlaps. 
The original idea for this opcode came from J McCartney's formlet class 
in SuperCollider, but this is possibly implemented differently(?).
    </p>
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      <div class="refsect1">
        <a id="idp110233504"></a>
        <h2>Syntax</h2>
        <pre class="synopsis">asig <span class="command"><strong>fofilter</strong></span> ain, xcf, xris, xdec[, istor]</pre>
      </div>
      <div class="refsect1">
        <a id="idp110235728"></a>
        <h2>Initialization</h2>
        <p>
      <span class="emphasis"><em>istor</em></span> --initial disposition of internal data space. Since 
filtering incorporates a feedback loop of previous output, 
the initial status of the storage space used is significant. 
A zero value will clear the space; a non-zero value will allow 
previous information to remain. The default value is 0.
    </p>
      </div>
      <div class="refsect1">
        <a id="idp110237648"></a>
        <h2>Performance</h2>
        <p>
      <span class="emphasis"><em>asig</em></span> -- input signal.
    </p>
        <p>
      <span class="emphasis"><em>xcf</em></span> -- filter centre frequency
    </p>
        <p>
      <span class="emphasis"><em>xris</em></span> -- impulse response attack time (secs). 
    </p>
        <p>
      <span class="emphasis"><em>xdec</em></span> -- impulse response decay time (secs). 
    </p>
      </div>
      <div class="refsect1">
        <a id="idp110241872"></a>
        <h2>Examples</h2>
        <p>
      Here is an example of the fofilter opcode. It uses the file <a class="ulink" href="examples/fofilter.csd" target="_top"><em class="citetitle">fofilter.csd</em></a>.

      </p>
        <div class="example">
          <a id="idp110243648"></a>
          <p class="title">
            <strong>Example 309. Example of the fofilter opcode.</strong>
          </p>
          <div class="example-contents">
            <p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
            <pre class="programlisting">
<span class="csdtag">&lt;CsoundSynthesizer&gt;</span>
<span class="csdtag">&lt;CsOptions&gt;</span>
<span class="comment">; Select audio/midi flags here according to platform</span>
-odac     <span class="comment">;;;realtime audio out</span>
<span class="comment">;-iadc    ;;;uncomment -iadc if realtime audio input is needed too</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o fofilter.wav -W ;;; for file output any platform</span>
<span class="csdtag">&lt;/CsOptions&gt;</span>
<span class="csdtag">&lt;CsInstruments&gt;</span>

<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">ksmps</span> <span class="op">=</span> 32  
<span class="ohdr">nchnls</span> <span class="op">=</span> 2
<span class="ohdr">0dbfs</span>  <span class="op">=</span> 1

<span class="oblock">instr</span> 1

kfe  <span class="opc">expseg</span> 10, p3<span class="op">*</span>0.9, 180, p3<span class="op">*</span>0.1, 175
kenv <span class="opc">linen</span> .1, 0.05, p3, 0.05
asig <span class="opc">buzz</span>  kenv, kfe, <span class="ohdr">sr</span><span class="op">/</span>(2<span class="op">*</span>kfe), 1
afil <span class="opc">fofilter</span> asig, 900, 0.007, 0.04
     <span class="opc">outs</span>  afil, afil 

<span class="oblock">endin</span>
<span class="csdtag">&lt;/CsInstruments&gt;</span>
<span class="csdtag">&lt;CsScore&gt;</span>
<span class="comment">; sine wave</span>
<span class="stamnt">f</span> 1 0 16384 10 1

<span class="stamnt">i</span> 1 0 10
<span class="stamnt">e</span>
<span class="csdtag">&lt;/CsScore&gt;</span>
<span class="csdtag">&lt;/CsoundSynthesizer&gt;</span>
</pre>
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        <p><br class="example-break" />
    </p>
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      <div class="refsect1">
        <a id="idp110247936"></a>
        <h2>Credits</h2>
        <p>
      </p>
        <table border="0" summary="Simple list" class="simplelist">
          <tr>
            <td>Author: Victor Lazzarini</td>
          </tr>
          <tr>
            <td>January 2005</td>
          </tr>
        </table>
        <p>
    </p>
        <p>New plugin in version 5</p>
        <p>Audio rate parameters introduced in version 6.02</p>
        <p>November 2013.</p>
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